High dynamic range (“HDR”) image sensors are useful for many applications. In general, ordinary image sensors, including for example charge coupled device (“CCD”) and complementary metal oxide semiconductor (“CMOS”) image sensors, have a dynamic range of approximately 70 dB dynamic range. In comparison, the human eye has a dynamic range of up to approximately 100 dB. There are a variety of situations in which an image sensor having an increased dynamic range is beneficial. For example, image sensors having a dynamic range of more than 100 dB are needed in the automotive industry in order to handle different driving conditions, such as driving from a dark tunnel into bright sunlight. Indeed, many applications may require image sensors with at least 90 dB of dynamic range or more to accommodate a wide range of lighting situations, varying from low light conditions to bright light conditions.
One known approach for generating an HDR image is to initiate a serial capture of images with an image sensor and then combine the best exposed portions of those images so that the HDR image is well-exposed. However, one drawback to this approach is the possibility that motion will be introduces between the serial images. For example, a subject (e.g. person or animal) in the imaged scene or a background feature (e.g. an analog clock) may introduce motion artifacts when the serial images are combined into the HDR image. Another drawback to the known approach is that motion from hand shake by the photographer may be introduced, especially when the image sensor is included within a mobile device. Hence, reducing motion artifacts in HDR images and/or reducing the time period required to generate HDR images is desirable.